Rotary encoders add precision and flexibility
Author : Terry Moss, general manager of knitter-switch UK
Typical rotary switching functions demanded by design engineers include level adjustment for lightning control, audio volume, valve or flow control etc. and function selection for system control.
Traditionally these operations have been the preserve of analogue components. The potentiometer for level control and the multi-position rotary switch for function selection. The increasing use of digital control techniques and demands for accuracy, repeatability and maximum functionality from man-machine interfaces has driven major developments in rotary coded switches which now offer competitive pricing, increased functionality, illumination and levels of robustness previously unheard of.
The largest and most obvious new market for replacing analogue rotary switches is in the arena of front panel control. Replacing a potentiometer with a rotary coded switch connected to digital control signals increases the accuracy and repeatability of the set-point, allows the user control of the level change between set-points and of the response curve characteristic (linear, logarithmic or custom). A single rotary coded switch may now be used to control a number of different functions by use of an integral push-switch, “soft-keys”, or external programming. This can simplify panel design, improve layout aesthetics and reduce component costs. In this way a single rotary coded switch may be enabled by “soft selection” to control a number of functions and levels which retain their independence and set level while other operations are carried out by the same switch. In the same way rotary coded switches may now be used to replace banks of push-buttons for single or interlocked switching functions.
In addition to front panel control, rotary coded switches are now also available as sub-miniature PCB mounted components frequently used to replace DIL switches and simplify board level programming. Able to be surface mount assembled and controllable by either screwdriver or shaft, PCB mounted rotary coded switches may be user accessible via access ports or only available to authorised technicians with direct board access.
Rotary coded switches are indexed giving users reassuring tactile “feel” and facilitating operation in low light levels or without having to be looked at in applications such as recording studios or when fitted to mobile telecoms and emergency equipment.
Manufactured using the most modern methods Rotary coded switches are now RoHS compliant, offer many mounting and automatic insertion options, extended operating temperature ranges and long life up to 30,000 operations.
A number of very desirable new features are now available including, shafts with optional push-button action and LED illumination, washable to IP67 and coding options which include BCD 10 position and hexadecimal 16 positions, each available with both real and inverse (complement) coding.
Applications for the latest generations of rotary coded switches include broadcast, pro-audio and lighting systems, automotive, medical equipment, industrial control, test and measurement equipment, PCB level programming, building automation systems, alarm and security equipment.
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